Although we tend to think of the Earth as an amazingly hospitable planet, at several times in the past it seems to have done its best to kill us all—or at least all of our ancestors. Several of the Earth's mass extinctions occurred around the time of elevated volcanic activity, but the timing has been notoriously difficult to work out; the fossil beds that track the extinction rarely preserve the evidence of volcanic activity and vice-versa.

A study that will appear in today's issue of Science provides a new window into the end-Triassic mass extinction, the event that ushered in the start of the era of the dinosaurs. The study provides a precise timing of events of the extinction through a combination of new dating work and a link to the Earth's orbital cycles preserved in rocks near Newark, New Jersey (because when you think end-Triassic, you think New Jersey, right?). The timing of events shows that the extinction occurred at the very onset of the volcanic activity that signaled the breakup of the supercontinent Pangea, but that life began to recover even as the later eruptions were taking place.

Thinking big

Volcanic activity takes place all the time, and while it can be devastating for the local environment (and you can use a very large definition of "local" for supervolcanoes), this isn't enough to set off a global extinction. For that, you need what are termed "flood basalt eruptions." These events are just what the name implies: molten rock comes flooding out of a rift and covers thousands of square kilometers in rock, often at depths of hundreds of meters. Then, before the Earth recovers, you do it all over again. The largest of these eruptions, which formed the Siberian Traps, has had the total volume of rock that erupted estimated at above a million cubic kilometers.

Events like these tend to kill stuff, and not just locally, where everything ends up buried under tons of rock. The eruptions send a lot of sulfur compounds into the atmosphere, which form a haze that reflects sunlight back to space. The result can create a sharp, temporary cooling in climate (think the Year Without a Summer on steroids). Once that clears out, the massive amounts of carbon dioxide that were also released kick in, swinging the temperatures up to new highs. The oceans don't get off lightly, either, as the same carbon dioxide causes a rapid ocean acidification, which makes it extremely difficult for any shelled creatures to survive.

Given that combination, it's no real surprise that the Siberian Traps eruptions set off the biggest mass extinction we know about, the end-Permian, which is commonly known as the Great Dying. Other large scale eruptions have also been associated with mass extinctions, including the one that killed the dinosaurs—that one produced India's Deccan Traps.

As noted above, getting the timing of everything down well enough to assign definitive blame is not easy; the role of the Deccan Traps eruptions in killing off the dinosaurs was only settled by finding something else to blame. But we now have a very good picture that ties eruptions nicely to the end-Triassic extinction, which wiped out some of the dinosaurs' competitors, allowing them to assume ascendancy.

Getting the timing right

The eruption that may have triggered the end-Triassic extinction was caused by the breakup of the supercontinent Pangea, and took place along the rift that would eventually form the Atlantic ocean. It left behind the Central Atlantic Magmatic Province (CAMP), which is now spread across four continents, from France and Spain through to West Africa on one side of the Atlantic, and along the US' East Coast and down into Brazil on the other. The CAMP was built from a series of eruptions that left behind giant layers of basaltic rock; residents of New York City can see one by looking across the Hudson at the Palisades of New Jersey.

Certainly, the eruptions were big enough to bring about global devastation. But did they? It has been hard to tell. Basalts don't typically include the sorts of minerals that allow us to do highly accurate dating through radioactive decay. And the basalts themselves contain no fossils, making it difficult to figure out how the timing of various events fit together.

The key to piecing things together came from an area in New Jersey called the Newark basin. Deposits in the basin contain a number of layers that turned out to be incredibly informative. To begin with, these included several distinctive layers of basalts caused by individual eruptions that contributed to the CAMP. These were interspersed with sedimentary deposits, some of which contained signs of life that allowed the process of extinction and recovery to be tracked. The sediments, however, also contained periodic changes that appear to line up with the Earth's orbital cycles (the same ones that drive the modern glacial cycles). Scientists hypothesized that these came about as local currents changed, altering the deposit of sediments, but there was no way to confirm that.

The new work involved drilling in to eight sites around the CAMP, a number of which yielded zircons associated with individual eruptions. These crystals, which are rarely associated with magmas, can be used for highly accurate uranium-lead dating. That gave them the timing of the individual eruptions, which could then be traced back to the Newark basin deposits. These confirmed that the dates predicted by orbital cycles lined up with those from the uranium-lead dates. With all this information in hand, it was possible to put together a chronology of both the extinction and the eruptions. (The authors refer to having a combination of geochronology and astrochronology.)

The data now suggests that it didn't take repeated heating-cooling cycles to start the extinction; the very first flood basalt eruption apparent in the CAMP seems to have started eliminating species. Three other major eruptions occurred over a 600,000 year period, but the first did the most damage. In fact, there are some indications that species were starting to recover even as the final eruptions were taking place.

Oddly, the CAMP may eventually play a role in reversing problems similar to the ones its formation caused. The rapid increase in CO2 we're currently creating is raising fears of a rapid ocean acidification that could lead to widespread extinctions as well. The rocks of the CAMP will react chemically with carbon dioxide and are being considered as a potential site of carbon sequestration.

Other large scale eruptions have also been associated with mass extinctions, including the one that killed the dinosaurs—that one produced India's Deccan Traps.

Out of curiosity, is this referencing the event ~65 million years ago? I was under the impression the consensus on the latter was still that it was due to an asteroid impact, has that changed?

I saw a show on Discovery, or Science, or one of those channels, where they theorized that it was a combination of the two. Some of the scientist they spoke with even suggested that the impact may have brought on the eruption. I wish I could remember the name of the program.

Out of curiosity, is this referencing the event ~65 million years ago? I was under the impression the consensus on the latter was still that it was due to an asteroid impact, has that changed?

I believe the author is merely stating the Deccan Traps are associated with theories surrounding the K-Pg boundary event (they are), not that they've been linked as the singular cause (they haven't). Note the following paragraph which reads:

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But, as we noted above, getting the timing of everything down well enough to assign definitive blame is not easy; the role of the Deccan Traps eruptions in killing off the dinosaurs was only settled by finding something else to blame. But we now have a very good picture that ties eruptions nicely to the end-Triassic extinction, which wiped out some of the dinosaurs' competitors, allowing them to assume ascendancy.

The early dinosaurs were a small, upstart species with good financial resources. They paid someone (aliens?) a shit-ton of money to eliminate the decadent Permian species. Continued protection payments ensured that things were good, very good, for the dinosaurs for a very long time. But eventually the dinosaurs got arrogant and started skipping payments. At some point (about 65 million years ago), the dinosaurs' "creditors" ran out of patience and engineered another extinction to pave the way for mammals. Although, they had a soft spot for feathered therapods and allowed them to live. The fact that therapods had given the creditors post-dated cheques may have helped, too.

Other large scale eruptions have also been associated with mass extinctions, including the one that killed the dinosaurs—that one produced India's Deccan Traps.

Out of curiosity, is this referencing the event ~65 million years ago? I was under the impression the consensus on the latter was still that it was due to an asteroid impact, has that changed?

Yes, it was a reference to the the dinosaur extinction event.

Iridium is found both in asteroids and volcanoes but Walter Alvarez claimed that the isotope of iridium found in the KT boundary is non-terrestrial strengthening the asteroid-killed-the-dinosaur hypothesis. They've also found shocked quartz in KT boundary samples dredged out of the Pacific which gives a sense of how large the explosion was.

It will be interesting to see if we can see somewhat similar effects (smaller, but hopefully still visible) of the flood basalt eruptions in the US Pacific Northwest between 17 million and 15.5 million years ago. While they were a bit smaller than the Siberian Traps (only about 200,000 cubic kilometers of basalt), that is still a HUGE amount and should have had a major impact...although not a global level extinction event.

It seems so odd that a meteor is the dominant theory from the demise of the dinosaurs. It makes so little sense as this wasn't such a big disaster. Short term and NA localized in it's devastation. Indian traps had a big impact, combined with a changing environment caused by the sequestering of carbon and oxygen from the air made into chalk by the bodies of microorganisms. Meteors are just so short term and localized, seems so odd that it has become the dominant theory. Keeps it simple?

It will be interesting to see if we can see somewhat similar effects (smaller, but hopefully still visible) of the flood basalt eruptions in the US Pacific Northwest between 17 million and 15.5 million years ago. While they were a bit smaller than the Siberian Traps (only about 200,000 cubic kilometers of basalt), that is still a HUGE amount and should have had a major impact...although not a global level extinction event.

To compare to a contemporary event, I looked up the current tally for Kiluea's eruption, ongoing since 1983. It has, in thirty years, expelled a mere 3.5 cubic kilometers of magma.

The early dinosaurs were a small, upstart species with good financial resources. They paid someone (aliens?) a shit-ton of money to eliminate the decadent Permian species. Continued protection payments ensured that things were good, very good, for the dinosaurs for a very long time. But eventually the dinosaurs got arrogant and started skipping payments. At some point (about 65 million years ago), the dinosaurs' "creditors" ran out of patience and engineered another extinction to pave the way for mammals. Although, they had a soft spot for feathered therapods and allowed them to live. The fact that therapods had given the creditors post-dated cheques may have helped, too.

I thought this was common knowledge. That it was aliens. Just sayin'.

Yes, the article headline is a mis-print. It should have read "Extinction that paved way for dinosaurs definitively linked to Vulcanism." But "somehow" the correct version of the title and the contents of the article were altered prior to dissemination. Just sayin'. Zap! Ow.

It wasn't that long ago, maybe as far back as 400 years ago human died of common cold and chicken pot. It convinced me similar virus out break caused the extinction of dinosaurs and even deaths to our earlier human spices. Sulfur compounds in the atmosphere is deadly but unlikely the cause of it.

It wasn't that long ago, maybe as far back as 400 years ago human died of common cold and chicken pot. It convinced me similar virus out break caused the extinction of dinosaurs and even deaths to our earlier human spices. Sulfur compounds in the atmosphere is deadly but unlikely the cause of it.

Wow, amazing. How did humans ever survive up until that time? How did their population continually grow given that huge obstacle?

A more realistic answer would be because human spices lived all over in different regions of the world. Virus could have got some of us but not all of us. If dinosaurs were concentrated living at one spot of the world that's the problem.

Edit: From that Wikipedia article the current extinction rate is estimated to be 100 to 10000 times higher than the background extinction rate between major extinction events. May you live in interesting times, indeed.

For a species that needs regular meals, you don't have to disrupt their food supply for very long in order to extinct them. A couple years of continuous winter can do it, as would be provided by a 10 km asteroid strike, or by a nuclear winter. Survivalism never caught on with the dinosaurs, and see what happened.

Nothing grow around/on volcanoes lavas. What do you do when you are out of foods? You move to where the fresh water is and go where the vegetations are. Human relocated themselves to another city/country to find jobs. Dinosaurs might have not been that smart of a spice compare themselves to human but they had lived for million years before their extinctions. That wasn't easy for them. I don't see how volcanoes killed the dinosaurs when they weren't even around and away from the volcanoes?

Nothing grow around/on volcanoes lavas. What do you do when you are out of foods? You move to where the fresh water is and go where the planets are. Human relocated themselves to another city/country to find jobs. Dinosaurs might have not been that smart of a spice compare themselves to human but they had lived for million years before their extinctions. That wasn't easy for them. I don't see how volcanoes killed the dinosaurs when they weren't even around and away from the volcanoes?

Which planet are you thinking about relocating to and what are the visa requirements?

It seems so odd that a meteor is the dominant theory from the demise of the dinosaurs. It makes so little sense as this wasn't such a big disaster. Short term and NA localized in it's devastation. Indian traps had a big impact, combined with a changing environment caused by the sequestering of carbon and oxygen from the air made into chalk by the bodies of microorganisms. Meteors are just so short term and localized, seems so odd that it has become the dominant theory. Keeps it simple?

Meteors of the size of the Chicxulub impactor are not a "localized" effect; they hose the whole planet in pretty much the same manner as flood basalts and for much the same reasons. Tons of dust in the air blocking light for years, molten rock all over the place giving off noxious chemicals and trashing the atmosphere, continent-wide flash heating induced firestorms instead of continent-wide lava floods, etc.

Don't forget the heat pulse effect, where all those billions of tons of vapourised material get blasted into the sky and then enter the atmosphere at suborbital speeds, heating up the air with their kinetic energy and causing anyone in the open to literally burst into flame.

It seems so odd that a meteor is the dominant theory from the demise of the dinosaurs. It makes so little sense as this wasn't such a big disaster. Short term and NA localized in it's devastation. Indian traps had a big impact, combined with a changing environment caused by the sequestering of carbon and oxygen from the air made into chalk by the bodies of microorganisms. Meteors are just so short term and localized, seems so odd that it has become the dominant theory. Keeps it simple?

Meteors of the size of the Chicxulub impactor are not a "localized" effect; they hose the whole planet in pretty much the same manner as flood basalts and for much the same reasons. Tons of dust in the air blocking light for years, molten rock all over the place giving off noxious chemicals and trashing the atmosphere, continent-wide flash heating induced firestorms instead of continent-wide lava floods, etc.

In the grand scheme of things yes they are a localized effect. The oh noes...iridium layer of multiples of parts per billion. Many times a hundred in some places the background level, a few time in places like Australia. In fact there is little evidence of disturbance in Australia.

Don't forget the heat pulse effect, where all those billions of tons of vapourised material get blasted into the sky and then enter the atmosphere at suborbital speeds, heating up the air with their kinetic energy and causing anyone in the open to literally burst into flame.

For that to be true, what kind of animals would survive? It's a pretty easy nul.

Animals that burrow, or live in the sea, or can get under cover. It's a short-lived thermal effect and its impact (no pun intended) would depend on size of the strike and where you where. I don't think it would be a global phenomena, though.

Looking at a globe, the Deccan traps at the time would have been approximately on the opposite side of the earth from the impact. I know that in experiments with kinetic energy transfer a mostly spherical object can channel impact energy to the opposite side through seismic shock. Could the Deccan Traps and other similar volcanic events be the "exit wound" of large scale impact events? If the crust is fractured sufficiently, lava would easily transfer to the surface until enough has built up to plug the leaks and halt the eruptions. This would create a double whammy of the impact event itself and all of the known dust and debris this would cause to the climate along with the huge impact of volcanism of this scale on the opposite side of the world.

The bulk of the volcanic eruption occurred at the Western Ghats (near Mumbai) some 65 million years ago. This series of eruptions may have lasted less than 30,000 years in total.[3]The original area covered by the lava flows is estimated to have been as large as 1.5 million km², approximately half the size of modern India.

About 1.5 million km sq. in 30,000 years. Or.....a meteor that hits once? Causes localized devastation in NA.

The world was also changing with Oxygen and Carbon Dioxide levels going down as the chalk was getting built up at the time by innumerable microorganisms shells littering the ocean floor with CaCO3. There was alot of pain going around.

These things aren't going to be localised. They are global, persistent and devastating.

But but....Australia really does show little evidence of destruction. Megatsunami, where? NA - it was in the Caribbean sea. Rapidly lowering temperatures for how long? Was there was little evidence of this. Wait how much evidence do we have? Acid rain...oh no...maybe but it would be local and short term. Modelling against what, how do we model this? Other ones that have happened that have the same level of estimation of size? Kara crater....70 million years ago, approx same size, 120 km across round - not egg shaped. Super destruction? Nope. Popigai or Chesapeake Bay, nope...hardly a ripple.

If you look at the numbers on that list, the gap between #3 and #4/5/6/7/8 is roughly 2X or more. Since #1 and #2 happened before life existed, it would be hard to point to the effects on life of a comparable bollide impact (that we know of).

If you look at the numbers on that list, the gap between #3 and #4/5/6/7/8 is roughly 2X or more. Since #1 and #2 happened before life existed, it would be hard to point to the effects on life of a comparable bollide impact (that we know of).

Right, Chixalub really is in a bit of its own class. There definitely have been other large impacts during the Phanerozoic, maybe even bigger ones, but each event is unique.

In any case, nothing says that one single cause explains a major extinction event. They are often complex drawn-out events, usually peaking at some point, but not clearly single events. Perhaps changes in the ecology of the Earth, geochemical changes, etc were already working against the fitness of dinosaurs, and then we have the Deccan Traps blasting holes in trophic networks, and finally a mountain-sized hunk of rock slams into the Earth at 40km/s and puts the dot on the i in Cretacious.

As for volcanism and supercontinents. I just learned that R.J, Stern has a longstanding theory on how supercontinental cycling ties into the expression of volcanism. I can't find any better ref than fig 4 here: http://www.utdallas.edu/~rjstern/pdfs/VW2SE08.pdf . Note that there are at least 4 types of volcanism as phases in full a cycle (rift related with massive outflux, ocean arcs during dispersal, continental arcs during assembly with another episode of massive outflux, collision related).

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the era of the dinosaurs. ... mass extinctions, including the one that killed the dinosaurs